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Back in February, the Opportunity rover celebrated its 5000th Martian day on the planet next door. And that’s a seriously amazing accomplishment, because Oppy was originally scheduled to operate for, like, three months.

In that time, it’s had to weather some pretty significant hardships, too, including a brush with death in 2007. That year, a planet-wide dust storm blocked out 99% of direct sunlight for weeks, which isn’t a great time when you’re powered by solar panels. Now, at this very moment, Oppy is fighting for its life again, thanks to another huge dust storm.

And we’re really hoping it’s going to be okay. Because after almost 15 years, a lot of people — myself included — are pretty attached to this thing. Opportunity landed on Mars in 2004, and it’s currently roving around the western edge of.

Endeavour Crater. Well, it would be roving, if it weren’t for a giant dust storm blotting out the Sun. Continent-sized dust storms happen every Martian year or so, and they’re caused by similar processes to storms on Earth — things like Sun-warmed air rising and picking up dust.

But unlike around here, these storms get so big every few years that Mars’s entire atmosphere turns into one giant light blocker. Opportunity hasn’t seen one of these giant dust storms since back in ‘07, and it’s difficult to know when exactly they’ll happen. But this one wasn’t totally unexpected.

About six months ago, astronomers predicted we’d see something this year as Mars’s orbit took it closer to the Sun and it got a bit warmer — among some other factors. NASA’s Mars Reconnaissance Orbiter first detected this storm on May 30th, and it now covers roughly a quarter of the planet’s surface. When we filmed this video on Tuesday, it wasn’t a planet-wide storm like we saw in 2007.

But from Oppy’s perspective, it’s a lot worse in terms of the amount of light being blocked out. In fact, this is the most opaque dust storm we’ve ever observed. And that’s not good news for the rover’s solar panels or its power levels.

On June 12th, NASA engineers attempted to communicate with Oppy, but did not hear back. This likely means the rover’s batteries are getting low and that it’s entered what’s called “low power fault mode”, where basically all subsystems are shut off except the master clock. The rover’s computer can occasionally wake up to check its power levels, but we won’t hear anything from it again until its batteries are full enough to exit that mode.

If it ever does. With so many systems shut down, the rover can’t keep itself warm, either. So if Opportunity goes without sufficient power for too long, it’ll basically freeze to death.

So, we’ll just wait to hear back from it… in silence… any day, now... Luckily, Endeavour Crater is warming up as the Southern Hemisphere heads into its summer season. And the dust storm is helping to keep the area warmer than it would otherwise be.

Current estimates suggest that Opportunity will survive the ordeal, but we don’t know exactly how long this storm’s going to last. Because there’s so little water in Mars’s thin atmosphere, dust can float around for months. So it will definitely be a while before Oppy’s solar panels will can get things fully operational.

If there’s any good news, though, it’s that the Curiosity rover will be fine. It’s also seeing skies dim way over in Gale Crater, but it relies on nuclear power, not solar panels. Along with NASA’s other robot immigrants, it will even do a little science while we wait for this storm to pass.

It, along with our three orbiters, will record things like temperatures and pressures at the surface and in the various parts of the atmosphere. They’ll also monitor the characteristics of the dust particles being flung around. Studying this storm will help scientists better understand Mars’s weather, which will hopefully allow us to predict future weather events one day.

But hopefully we won’t have to sacrifice one of our favorite robots to get there. Now while Mars is whipping dust around, a paper published in Nature Geoscience this week reports that the wind on our other planetary neighbor is changing the length of its days. Of all the planets in our solar system, Venus has — by far and away — the longest day.

It’s about 243 Earth days long. Yeah. 8 months. But weirdly, measurements can’t seem to pin down exactly how long it is.

They aren’t off by much — less than 10 minutes — but it’s enough of a curiosity that astronomers are trying to determine what’s happening. One team hypothesized that the difference might be partially caused by the interactions between Venus’s thick atmosphere and its hot nightmare of a surface. Their idea was inspired after Japan’s Akatsuki spacecraft observed a super long, bow-shaped feature at the top of the atmosphere in 2015.

See, Venus’s atmosphere rotates around the planet 60 times faster than the ground beneath it — although we don’t know why. But that bow-shaped structure is somehow relatively stationary above a mountainous region on the continent called Aphrodite Terra. The team ran computer simulations of Venus’s atmosphere and confirmed that the structure is most likely an atmospheric gravity wave caused by the surface topography.

Gravity waves aren’t the same as gravitational waves — the ripples in spacetime that happen when things like black holes collide. Instead, they’re waves made of air that are forced to ripple up and down. This can happen after air hits a mountain and gets shot upward, then pulled back down by gravity.

At that point, the air’s momentum keeps it bobbing up and down until it settles back to equilibrium. The simulations showed that the amount of torque these waves exert on Venus’s surface are enough to cause the planet’s rotation to vary by a couple of minutes. It’s not enough to explain all of the differences in measurement, but it was a fairly simplified model.

With more data, tracking the change in the length of day will ultimately allow astronomers to figure out why Venus spins the way it does, which we don’t actually have a definitive answer for. Admittedly, another way we could try and solve that mystery is by sending a lander or rover to Venus… but it’s terrible there. Opportunity is having a hard enough time on Mars where it’s relatively static and lead isn’t a liquid.

Thanks for watching this episode of SciShow Space! And a special thanks to our President of Space, Matthew Brant! Thank you so much for your support.

If you’d like to keep up with the latest news from around the solar system — and the rest of the universe — you can go to youtube.com/scishowspace and subscribe. We post a news episode like this every Friday. [ ♪ Outro ].